>Hmm. So, could one then just make a flat-bottomed panel, carefully
>aligned with the incoming airflow, with a top geometry that doesn't
>transmit shock waves very well, and carry that underneath the wing? (Or
>maybe have a flat-bottomed wing, likewise aligned, with the engines in or
>above the wing so as not to disrupt the bottom.)
You have to worry about shock waves reflected off solid surfaces as well
as those heading downward directly. And if you want to eliminate wave
drag, you've got to cancel out shocks heading upward as well as those
going down. Dealing with all of this tends to make the lower surface a
mirror image of the upper one... which does the shock cancellation quite
nicely (it's called a "Busemann biplane" and it's been known since the
1940s), but unfortunately the symmetry eliminates all *lift*.
Shockless supersonic shapes like the Busemann biplane have been known for
a long time, but they've been an obscure curiosity relegated to dusty
books because there seemed to be no way to generate lift with one.
Merely not throwing a shock wave *down* is a less stringent requirement,
although with less payoff too. I think such configurations got looked at
once sonic boom became a major concern, although I'm not up on the exact
history here; my impression is that people eventually concluded that you
could not build a reasonably efficient supersonic wing with a flat bottom
exactly parallel to the flow.
Henry Spencer
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